Recently, an information and communication technology (ICT) is increasingly applied in a work machine such as a bulldozer. For example, there is a work machine or the like mounted with a global navigation satellite systems (GNSS) and the like and adapted to: detect own position; compare such positional information with current topographical data indicating a current topography of a work site; and find a position, a posture, or the like of a work unit by performing arithmetic processing (refer to Patent Literature 1, for example). The current topographical data is managed by, for example, an external server and the like, and transmitted to the work machine from such a server. The work machine receives one kind of current topographical data transmitted from the server, and performs arithmetic processing and the like.